Users can’t reasonably be expected to switch smartphone hardware just because of an app. The smartphone hardware market has its own constraints (people generally own only one at a time, they upgrade it every couple of years at a cost of several hundred dollars, etc). Apple may have legitimately earned its position in that hardware market by making products people want, but it’s not legitimate for them to use that dominance to control wholesalers’ access to consumers in a separate marketplace: music streaming. In that marketplace, the relative success of Apple Music vs Spotify should be based on consumer preferences for those services, not on which company also happens to dominate a separate marketplace. See also: Microsoft using its OS market dominance to control the web browser market.